lkl: remove string functions duplicate implementation

Now that we have the ability to set kernel config options per host
built we can avoid duplicating the implementation for string functions
that may be provided by the host (e.g. memcpy, memset).

Signed-off-by: Octavian Purdila <tavip@google.com>

Author: tavip

arch/lkl/Kconfig

@@ -182,3 +182,24 @@ config BUILTIN_CMDLINE
 	  image and used at boot time. The command line provided to
 	  lkl_start_kernel is appended to this string to form the full
 	  command line.
+
+config LKL_HOST_MEMCPY
+	bool "Host provides memcpy"
+	default n
+	help
+	  This options should be set (in tools/lkl/Makefile.autoconf)
+	  if the host provides a memcpy implementation.
+
+config LKL_HOST_MEMSET
+	bool "Host provides memset"
+	default n
+	help
+	  This options should be set (in tools/lkl/Makefile.autoconf)
+	  if the host provides a memset implementation.
+
+config LKL_HOST_MEMMOVE
+	bool "Host provides memmove"
+	default n
+	help
+	  This options should be set (in tools/lkl/Makefile.autoconf)
+	  if the host provides a memmove implementation.

arch/lkl/include/asm/string.h

@@ -7,70 +7,35 @@
 
 /* use __mem* names to avoid conflict with KASAN's mem* functions. */
 
+#ifdef CONFIG_LKL_HOST_MEMCPY
 #define __HAVE_ARCH_MEMCPY
 extern void *memcpy(void *dest, const void *src, size_t count);
 static inline void *__memcpy(void *dest, const void *src, size_t count)
 {
-	char *tmp = dest;
-	const char *s = src;
-
-	if (lkl_ops->memcpy)
-		return lkl_ops->memcpy(dest, src, count);
-
-	/* from lib/string.c */
-
-	while (count--)
-		*tmp++ = *s++;
-	return dest;
+	return lkl_ops->memcpy(dest, src, count);
 }
+#define memcpy(dst, src, len) __memcpy(dst, src, len)
+#endif
 
+#ifdef CONFIG_LKL_HOST_MEMSET
 #define __HAVE_ARCH_MEMSET
 extern void *memset(void *s, int c, size_t count);
 static inline void *__memset(void *s, int c, size_t count)
 {
-	char *xs = s;
-
-	if (lkl_ops->memset)
-		return lkl_ops->memset(s, c, count);
-
-	/* from lib/string.c */
-
-	while (count--)
-		*xs++ = c;
-	return s;
+	return lkl_ops->memset(s, c, count);
 }
+#define memset(s, c, n) __memset(s, c, n)
+#endif
 
+#ifdef CONFIG_LKL_HOST_MEMSET
 #define __HAVE_ARCH_MEMMOVE
 extern void *memmove(void *dest, const void *src, size_t count);
 static inline void *__memmove(void *dest, const void *src, size_t count)
 {
-	char *tmp;
-	const char *s;
-
-	if (lkl_ops->memmove)
-		return lkl_ops->memmove(dest, src, count);
-
-	/* from lib/string.c */
-
-	if (dest <= src) {
-		tmp = dest;
-		s = src;
-		while (count--)
-			*tmp++ = *s++;
-	} else {
-		tmp = dest;
-		tmp += count;
-		s = src;
-		s += count;
-		while (count--)
-			*--tmp = *--s;
-	}
-	return dest;
+	return lkl_ops->memmove(dest, src, count);
 }
-
-#define memcpy(dst, src, len) __memcpy(dst, src, len)
-#define memset(s, c, n) __memset(s, c, n)
 #define memmove(dst, src, len) __memmove(dst, src, len)
+#endif
 
 #if defined(CONFIG_KASAN)
 

arch/lkl/lib/string.c

@@ -14,22 +14,28 @@
 #undef memset
 #undef memmove
 
+#ifdef __HAVE_ARCH_MEMCPY
 __visible void *memcpy(void *dest, const void *src, size_t count)
 {
 	return __memcpy(dest, src, count);
 }
 EXPORT_SYMBOL(memcpy);
+#endif
 
+#ifdef __HAVE_ARCH_MEMSET
 __visible void *memset(void *s, int c, size_t count)
 {
 	return __memset(s, c, count);
 }
 EXPORT_SYMBOL(memset);
+#endif
 
+#ifdef __HAVE_ARCH_MEMMOVE
 __visible void *memmove(void *dest, const void *src, size_t count)
 {
 	return __memmove(dest, src, count);
 }
 EXPORT_SYMBOL(memmove);
+#endif
 
 #endif

tools/lkl/Makefile.autoconf

@@ -89,6 +89,9 @@ define posix_host
   $(if $(filter $(1),elf32-i386),$(call set_autoconf_var,I386,y))
   $(if $(strip $(call find_include,jsmn.h)),$(call set_autoconf_var,JSMN,y))
   $(if $(filter %,$(zpoline)),$(call zpoline_conf,$(zpoline)))
+  $(call set_kernel_config,LKL_HOST_MEMCPY,y)
+  $(call set_kernel_config,LKL_HOST_MEMSET,y)
+  $(call set_kernel_config,LKL_HOST_MEMMOVE,y)
 endef
 
 define nt64_host